Opened paints

It's better to dispense only as much as you need for a particular job, thin it and discard any leftovers than it is to thin an entire jar of paint.

I'd suggest, in the case of thinned paint, that you should be prepared to use it within about a week, or up to two weeks max after thinning. 

If you elect to keep left over paint, do so in a container that offers the least amount of unused capacity. Air and thinned paint are not good friends.

Decant to into smallest container possible.

felipejcg wrote:

Once i thin a paint how long does it last?

It depends on the paint.  With ModelMaster enamel, it goes bad very quickly, usually a few days.  The only reason I might want to save some thinned enamel, is when I have made a custom color mix and want to keep some around for some last minute touchups.

Acrylics, on the other hand seem to last indefinitely.  I have thinned mixes of of Tamiya, ModelMaster Acryl or combinations of both Tamiya and ModelMaster Acryl acrylics that have literally kept for months or years.  The stuff still separates into layers of thinner and color, but unlike enamels, I can simply stir the thinner and paint together and it is good as new.

Andy

That's funny.  I use Model Master enamels all the time and have never had that problem.  I've thinned the enamels and left them sit for 6 months with no problems.  What thinner do you use?  I always thin with Testors brand thinner for airbrushing.

-Jesse

I've used both cheap hardware store thinner as well as ModelMaster Airbrush Thinner.  Actually, that was one of the reasons I decided to experiment with buying ModelMaster Airbrush Thinner.  I thought that the generic thinner might be fine for airbrushing, but not so good for long term storage of thinned paints, while the brand specific thinner might allow for long term storage.  In my case, it hasn't worked out that way.

What happens with my thinned enamels, is that the paint pigments settle out so there is a clear layer of thinner on top with the heavy paint below.  Once that happens, even if I stir the two layers together, it seems as though the pigment particles stay clumped together no matter how much shaking and stirring I do.  If I try and airbrush the stuff, it just clogs the airbrush and never does paint right.

Andy